Valence bond theory and hybridization

Question 1

Reduced octects

Answer 1

dont need 8 electrons in their octect

Question 2

Using Quantum Theory to Explain Ionic Bonding

Answer 2

Transfer of electrons from one orbital to another
E.g. NaCl
Losing 1 electron will allow sodium to have a stable octet (2s22p6) like the noble gas neon
Gaining 1 electron fills will allow chlorine to have a stable octet (3s23p6) like the noble gas argon

Question 3

How do bonds form?

Answer 3

**The valence bond theory/model **or atomic orbital model was developed by Linus Pauling in order to explain how atoms come together and form molecules.
The model theorizes that a covalent bond forms when two orbitals overlap to produce a new combined orbital containing two electrons of opposite spin.

Question 4

Energy changes with bonds

Answer 4

This overlapping results in a decrease in the energy of the atoms forming the bond. (having an orbital with only one electron is a higher energy state)
The shared electron pair is most likely to be found in the space between the two nuclei of the atoms forming the bonds.

Question 5

new combined orbital will contain…

Answer 5

The newly combined orbital will contain an electron pair with opposite spin just like a filled atomic orbital.

Question 6

Hybridization

Answer 6

Chemical bonds in molecules such as methane can be explained by the concept of hybrid orbitals

Hybridization is the process of forming hybrid orbitals of at least two different orbitals
Atomic orbitals will hybridize (mix) to form orbitals for bonding
The atoms are responding as needed to give the minimum energy for the molecule
Orbitals MUST hybridize for atoms to bond together!

Question 7

Hybrid Orbitals

Answer 7

Consider beryllium:
In its ground electronic state, it would not be able to form bonds because it has no singly-occupied orbitals.
But if it absorbs the small amount of energy needed to promote an electron from the 2s to the 2p orbital, it can now form two bonds

Consider beryllium:
The 2s and the 2p electrons each have different energies
After one electron gets promoted to the 2p orbital, the 2s and one of the 2p orbitals will hybridize (mix) so that both electrons have the same energy for bonding

Question 8

hybridization layer (orbitals)

Answer 8

There are now TWO (2) IDENTICAL sp hybrid orbitals, of equal energy, with one electron each
The sp orbitals are higher in energy than the 1s orbital but lower than the 2p

Question 9

lone pairs

Answer 9

ALL electrons must be in an orbital! (even lone pairs!!)

Question 10

single bonds

Answer 10

A sigma bond (σ) - a bond created by the end-to-end overlap of atomic orbitals

Question 11

Double Bonds

Answer 11

A pi (π) bond - is a bond created by the side by side (or parallel) overlap of two un-hybridized p orbitals (one from each neighboring atom).

A double bond contains 1 sigma and 1 pi bond

Question 12

how do pi orbitals look like on the atom?

Answer 12

The p orbitals of each carbon atom overlap sideways to form a pi bond

The unhybridized p-orbital is perpendicular to the plane of the hybridized orbitals.

Question 13

Triple bonds

Answer 13

Partial hybridization can also be used to explain how triple bonds form
A triple bond contains 1 sigma and 2 pi bonds (2 un-hybridized p orbitals – on each atom)
The unpaired electrons in the two un-hybridized p-orbitals will form two pi bonds
Triple bond = 1 sigma bond + 2 pi bonds